Log periodic electron discharge device

ABSTRACT

A log periodic electron discharge device is disclosed which, in one form, is an RF amplifier including a conical slow-wave circuit defining an electron beam path therethrough. The slowwave circuit tapers in a log periodic manner for interaction with an electron beam passing therethrough. An input signal is coupled into the circuit to selectively energize a region therein based on the input signal frequency, and the beam is modulated. This modulated beam passes into a further part of the circuit to selectively energize a predetermined region therein and amplified power is taken off the circuit.

Unite States Patent Donald A. Wilbur Tierra Verde, Fla. 582,879

Sept. 29, 1966 Mar. 23, 1971 General Electric Company [72] Inventor [21 Appl. No. [22] Filed [45] Patented [73] Assignee [54] LOG PERIODIC ELECTRON DISCHARGE DEVICE 27 Claims, 7 Drawing Figs.

[52] US. Cl SIS/3.5, 315/36, 330/43, 333/31, 333/34 [51] Int. Cl H0lj 25/34 [50] Field ofSearch 315/3,3.5, 3.6, 5.43, 39.3; 330/43; 333/31, 31 (A), 34; 343/7925 [56] References Cited UNITED STATES PATENTS 3,020,439 2/ 1962 Eichenbaum 315/35 FOREIGN PATENTS 969,886 3/1950 France 315/36 OTHER REFERENCES Log-Periodic Transmission Line Circuits" Part I: One Port Circuits by Duhamel et al. IEEE Transactions on Microwave Theory and Techniques Vol. MTT- 14, No. 6 June 1966 pps. 264- 274 Relied upon.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-Saxfield Chatmon, Jr.

AttorneysNathan J. Cornfeld, Frank L. N euhauser, Oscar B.

Waddell, John P. Taylor and Joseph B. Formon ABSTRACT: A log periodic electron discharge device is disclosed which, in one form, is an RF amplifier including a conical slow-wave circuit defining an electron beam path therethrough. The slow-wave circuit tapers in a log periodic manner for interaction with an electron beam passing therethrough. An input signal is coupled into the circuit to selectively energize a region therein based on the input signal frequency, and the beam is modulated. This modulated beam passes into a further part of the circuit to selectively energize a predetermined region therein and amplified power is taken off the circuit.

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LOG PERIODIC ELECTRON DISCHARGE DEVICE This invention relates to a log periodic electron discharge device and more particularly to a log periodic electron beam device including interaction between an interaction structure having progressive interaction characteristics which vary in a log periodic manner, and an electron beam passing therethrough. Interaction takes place at selected regions along the interaction structure depending on the frequency characteristics of an input signal wave to provide for example a very high RF power output over a wide frequency band.

Extensive efforts have been expended to increase the operating bandwidth of microwave RF tubes in general. Particularly, high power RF tubes such as velocityand/or density-modulated electron beamtubes, including klystrons and traveling wave tubes, are generally compromises between inherent bandwidth limitations and power output. For example, a multicavity velocity-modulated electron beam klystron usually has a very high power output in a range of up to several megawatts but with a maximum relative bandwidth of only about percent. On the other hand typical traveling wave tubes generally have lesser power output but increased bandwidth. Hybrid combinations of klystrons and traveling wave tubes may provide more bandwidth but with a sacrifice of other prime considerations such as output uniformity, gain, etc. Due to the continuous development of more sophisticated electron apparatus, there is an increasing demand, for exampie, for a single tube type having both a uniform high power output and a wide frequency band.

Accordingly, it is an object of this invention to provide an improved electron discharge device.

It is another object of this invention to provide a log periodic electron beam modulating device.

It is yet another object of this invention to provide an improved log periodic RF amplifier having a high power output over a wide frequency band.

It is still another object of this invention to provide an improved log periodic klystron-type amplifier.

It is yet another object of this invention to provide an improved log periodic slow-wave circuit-type amplifier.

It is still another object of this invention to provide a log periodic amplifier having a tapering interaction structure.

It is a further object of this invention to provide an improved log periodic amplifier having a conical or frustoconical interaction structure with an electron beam passing therein.

It is another object of this invention to provide a biconical log periodic amplifier.

It has been discovered that log periodic principles may be applied to interaction structures or circuits, particularly for RF power amplification for very wide band applications. In this invention, log periodic or log periodic manner" are terms applicable to an array of interaction circuits, elements, or regions which are dimensioned and positioned such that electrical properties, i.e., impedance at each element or region repeat periodically with the logarithm of an operating frequency, e.g., input signal frequency.

Briefly described, this invention is one of its preferred forms, comprises an interaction structure such as a slow-wave circuit having interaction characteristics therealong which vary progressively in a log periodic manner. An electron beam is caused to pass through the interaction circuit for selective interaction at one or more regions thereof depending on input signal frequency. More specifically, one preferred embodiment of this invention includes a series of spaced resonant klystron-type cavities and interaction gaps for interaction with an electron beam passing therethrough. Each resonant klystron cavity in the series-spaced array differs in its effective size and resonance in geometric progression from a larger resonant cavity to a smaller resonant cavity along the extended array.

Accordingly, log periodic manner is a term applied to an interaction structure whose defined interaction characteristics therealong vary periodically in geometric progression. The variance is predicated to a large extent on dimensions. For example, in a slow-wave circuit including an extended array of coupled klystron-type resonant cavities, each cavity is preferably similar to its preceding cavity with the exception that significant dimensions are reduced or increased as the case may be. The result is a spaced array of cavities of different resonance, the resonant differences between cavities corresponding to a series progression. In a slow-wave circuit utilizing a helix for example successive sections or region are progressively reduced in diameter while turn density increases. The log periodic principle has been previously applied to antennaefsee Mayes, Broadband Backward Wave Antennas, The Microwave Journal, Jan. 1963, Vol. VI, No. l and the references cited therein.

This invention will be better understood when taken in connection with the following description and the drawings in which:

FIG. 1 is a cross-sectional illustration of one preferred embodiment of this invention as a log periodic klystron amplifier;

FIG. 2 is a cross-sectional illustration of a further preferred embodiment of this invention as applied to a traveling wave tube circuit;

FIG. 3 is a biconical modification of this invention;

FIG. 4 is a biconical modification wherein the circuit of the first half of FIG. 3 is replaced with the traveling wave circuit of FIG. 2;

FIG. 5 is a biconical modification wherein half of the circuit of FIG. 3 is replaced with the circuit of FIG. 1;

FIG. 6 is a biconical modification wherein each half-section includes the circuit of FIG. 1; and

FIG. 7 is a biconical modification wherein each half-section includes the traveling wave circuit of FIG. 2.

Referring now to FIG. 1, there is illustrated the log periodic principle of this invention as incorporated in a klystron-type amplifier l0. Klystron-type amplifier 10 includes an interaction circuit comprising an extended array of a number of adjacent or coupled coaxial cylindrical reentrant resonant cavities 11 through 21 distributed along an illustrated tapered section 22. The extended array of coupled cavities of this invention in the tapered section 22 is based upon or embodies a logarithmic progression which provides each succeeding cavity with geometrically progressively changing operating characteristics with respect to its resonance. In one form of this invention the logarithmic periodicity and geometric progression is applied in one sense with each adjacent cavity being generally similar in configuration with a preceding cavity with the exception of being smaller in a number of significant dimensions by a constant factor which may be denoted as p. This logarithmic periodicity with geometric progression is preferably extended over a substantial number of adjacent cavities in the klystron amplifier and preferably in excess of about three cavities. The logarithmic factor p as applied to a cavity diameter for example would include a first cavity having a diameter of for example 1.0 with the next succeeding cavity having the same position diameter of 0.9, and the next succeeding cavity of 0.81 etc. Accordingly, the geometric progression or the log factor p in such an instance is defined as 0.9 or alternately as a continuous 10 percent decrease along the array. The same factor may be applied to all significant dimensions of the cavities in the geometric progression.

One form of defined interaction circuit in accordance with the log periodic principle includes each cavity 11 through 21 of the log periodic interaction structure having common or partition walls 23 through 32 of decreasing diameter with respect to the side or bounding wall 33. By reason of the decreasing diameters of the partition walls and the axial distance therebetween, the sidewall 33 takes on, as a surface of revolution, a conical or tapering or frustoconical configuration. This taper, exaggerated in FIG. 1 for the purpose of clarity, includes tapering from a larger diameter at the input end 34 of the klystron-type amplifier to a smaller diameter in a direction toward the output end 35 of the klystron-type amplifier 10. Each succeeding cavity may be smaller than a preceding cavity in stepwise progression so that a series of short cylindrical bounding wall 33 sections define an outer wall, the

step progression being a geometric progression and not an approximation.

The geometric progression also includes adjacent cavities whose density or number of cavities per unit length of interaction structure increases from the input end 34} toward the output end 35. The axial distance between adjacent walls 24 and 25 for example is less than the corresponding distance between walls 23 and 24.

Cavities 11 through 21 also include as a part of their cavity construction, short tubular transverse wall sections 36 through 46 which are defined as reentrant or klystronlike drift tubes. Each of these reentrant tubes is spaced from preceding and succeeding reentrant tubes to provide well-known klystrontype interaction gaps 47 through 57. Reentrant tubes 36 through 46 are formed as short cylindrical sections to define a longitudinal channel or electron beam path 58. Reentrant tubes 36 through 46 are also short cylindrical sections of decreasing axial lengths in geometric progression so that the interaction gaps 47 through 57 which are defined between adjacent drift tube sections are also involved in the geometric progression principle, in that their axial spacings also decrease from the input end of the tube 34 toward the output end 35 of the tube 10. These gaps logarithmically decrease and become smaller in geometric progression in the same manner as the cavities become smaller.

It is understood that providing cavities in the geometric progression as described will soon involve a very great number of cavities of very small dimensions. For example, and theoretically speaking, the number and size decrease of cavities approaches infinity at the apex of the taper of a conical section. When the number of cavities becomes disproportionately large and of disproportionately smaller sizes, their effectiveness becomes greatly decreased and an arbitrary but compromising point is reached where the device is terminated and the array of cavities is terminated or ended substantially before the apex point may be reached. This results in the need for a termination of a kind which will reduce end losses and other undesirable effects from the great number of disproportionately small cavities. Accordingly, section 22 of device 10 which is illustrated as a tapered section may be terminated in the general form of a frustum where the defined array of cavities cease a predetermined distance before the apex is reached. Device 10 may also be terminated by a preferred method of termination, as disclosed in copending application Ser. No. 582,895 by Thal, filed Sept. 29, 1966, now US. Pat. No. 3,527,976. The termination of the mentioned copending application includes a short cylindrical section having a number of succeeding equal cavities not embodying the geometric progression. For example, the cylindrical section includes a plurality of cavity resonators all of which are similar in all respects in that their partition walls, drift tubes and interaction gaps, etc., are all equal to one another. A klystron-type amplifier as illustrated in FIG. 1 for example should have at least three cavities in section 22.

In order to provide an electron beam passing through channel 58 an electron gun structure 59 is utilized at the input end 34 of klystron device 10, and a corresponding electron collector 60, as well known in the art, is utilized at the output end of the klystron 10. Electron gun structure 59 is exemplary of a number of suitable gun structures including, for example, the gun structure as disclosed in US. Pat. No. 3,046,442 to Cook. See also J R. Pierce, Theory and Design of Electron Beams, Norstrand Co., lnc., New York, N. Y., 1949. In FIG. 1, electron gun structure 59 includes a cylindrical electrically insulating section 61 which is mounted concentrically on the input wall 62 adjacent cavity 11 and is also concentric to the electron bearn channel 58. A transverse wall 63 is fixed to section 6ll to support the electron gun emitter 64 therein. Electron gun emitter 64 as known in the art includes an electron emissive surface usually including a combination of a barium compound and a refractory metal matrix. This surface which is denoted as surface 65 in FIG. 1 is of a concave design ordinarily as large as or larger than the beam channel and is battery 69.

An electrical shroud-forming structure having an outwardly flared lip 71 thereon circumferentially surrounds the concave emissive surface member 65 and is electrically connected to the transverse wall 63. An annular block member 72 defines the entry portion of the electron beam path 58 and is positioned concentrically thereto and concentrically the structure of electron gun emitter 64. These structures 70 and 71, and their adjacent surfaces 72 and 73, are so formed so that the electric field existing therebetween exerts a controlling influence on the electron beam to control the beam shape as it enters member channel 56.

The collector 60 as well as the remaining interim parts of klystron device 10 are electrically conductive so that transverse wall 63 is connected to the negative side of a suitable source of power, such as battery 74 while the cavities and the collector 60 are connected to the positive side of the battery 74. Electrons are therefore emitted from surface 65 and are suitably formed by shroud 71, annular block 72, and the electrical field therebetween, as an electron beam 75 to pass down the electron beam path 58 and to be collected by the collector 60. Collector 60 may be a suitable hollow block or casing member defining an electron-collecting cavity or cavity surface 76 therein, and may also have suitable fluid-cooling means associated therewith as known in the art.

Means to control the cross section of an electron beam over an axially extending length are well known in the art. These may include magnetic, electrostatic, or electromagnetic or other electrical field focusing arrangements which provide the proper controlling action on the beam. In one form of this invention an electrical focusing solenoid 77 is employed which extends axially along the beam path 57. The number of turns or turn density of the coil of solenoid 77 is selected in conformance with the diameter of beam 75 to provide a beam cross section which is desired. Solenoid 77 may also be tapered to be closely adjacent the bounding wall 33.

Permanent magnet focusing or control is equally applicable to this invention and may include one or more magnet assemblies arrayed along the axis of the klystron to provide the desired magnetic field. A number of electromagnets, permanent magnets, or electrostatic focusing means or combinations thereof, may be employed to provide a beam whose diameter and cross section are conductive to the desired interaction.

A transmission line 78 or other similar coupling means is employed to couple power into and out of the klystron amplifier 10. For example, a transmission line is illustrated in FIG. 1 in the form of an electrically conductive rod 79 which passes through the transverse walls of successive cavities in the klystron amplifier 10. At the input end 34 device 10 includes a convenient tubular input section 80 through which rod 79 passes. Rod 79 is also electrically insulated from tubular section 80 by means of a ceramic window-type seal 81 therebetween. At the output section 35 there is also provided a tubular output section 80' and ceramic window seal 81. Rod 79 is also conveniently insulated from each of the partition walls through which it passes so that it is electrically insu lated entirely from klystron-type device 10. A number of looptype couplers may also be employed in this invention in lieu of the transmission line as described.

Ordinarily in the operation of the device of this invention the electron gun 59 is suitably energized to provide a beam 75 passing through successive cavities and interaction gaps for collection by collector 60. A power signal of given frequency is coupled into device 10 through rod 79 at the input or cathode end 34 of device 10. By means of rod 79 the input signal enters the tapered section 22 and selectively energizes a first region of one or more cavities therein whose resonant frequencies closely correspond to the frequency of the input signal. Strong interaction in a klystron manner takes place in the interaction gaps associated with these cavities and energy is coupled to the beam. At a further region along the interaction structure one or more cavities become receptive to beam power and the power from the beam is coupled back to the transmission line as amplified power output. The term region" is employed to denote a part or section of an axially extending interaction structure and constitutes the selected one or more resonant cavities which are responsive to an input signal.

As a further example, a higher frequency signal progresses down rod 79, passing by one or more of the larger cavities which may not be resonant at the frequency of the input signal, until it reaches a portion or region of device in the tapered section 22 thereof where cavities are near their resonance at the frequency of the input signal. These latter cavities which have become selectively responsive based on input frequency become effective in the known manner and strong interaction takes place in the affected interaction gaps associated with these cavities. As the input signal progresses further toward the smaller end of the device and of section 22 to cavities which are also not resonant, the interaction diminishes preferably to a negligible level. The amplified signal is then coupled out of device 10 through the rod 79 at the output end.

The operation of this invention may be alternately described as follows. At a specified frequency one unit of power traveling along a semi-infinite length of the cold structure (or a properly terminated finite length) produces a particular pattern of voltage at each interaction gap. If the applied frequency is divided by p, the logarithmic progression, the entire pattern is moved one section to the right or toward the smaller end of the device. Provided that the beam diameter is scaled by p at each section while the total current and voltage remain constant, the electron beam behavior scales in the same manner as the circuit behavior. For a circuit of the type shown in FIG. I, interaction'between the circuit wave and the beam will take place primarily in the portion of the tube where the resonant frequencies of the cavities are close to the applied frequency. In this region the cold circuit is nonpropagating and the signal is coupled from cavity to cavity by the electron beam in the manner of a klystron. As the frequency is increased this active portion moves toward the smaller end of the tube where the beam couples an amplified signal to the circuit for power output. If the tube is sufficiently long, the input and output connectors will be located in regions of weak interaction for all frequencies in the desired band. Thus, the end effects are not serious and the gain-frequency response repeats itself each time the frequency is divided by p.

A further modification of this invention is illustrated in FIG. 2. Referring now to FIG. 2, there is shown a traveling wavetype tube 82 incorporating the log periodic principle of this invention. As described in FIG. I, an electron gun structure 59 provides an electron beam passing through a typical helix circuit 83 of a traveling wave tube to a collector 60. The helix circuit includes the log periodic principle by having turns which decrease in diameter in geometric progression toward one end of the device, and at the same time the turn density or number of turns per unit length geometrically increasing toward the same end of the device. Both the wire thickness and width may also vary. The long periodic concept may be suitably approximated by a number of diminishing straightline sections or other structure-varying means which affect interaction in the log periodic manner. Since continuation of the log periodic principle leads to a theoretically infinity tapering helix, the device may be suitably terminated similar to that as described for FIG. 1.

The overall or general traveling wave tube operation of the device of FIG. 2 is the same as for other traveling wave tubes. However, the log periodic principle as applied to the helix or slow-wave circuit affects the operation of the device in a manner similar to the effect as described for the log periodic klystron-type device 10 in FIG. 1. For example, an input signal of a given frequency is introduced into the slow-wave helix circuit 83 by means of connector portion 84, and selectively energizes a portion or region thereof responsive to the frequency of the input signal. Strong interaction at this region takes place and RF energy is coupled to'the beam for amplification. Amplified RF energy is coupled out of the beam at a region of the helix further advanced along the helix at a region where the amplified signal may again be passed to the helix. Power output is taken from end 85 of helix circuit 83 at the output end 35. The helix interaction circuit is one example of numerous similar and equivalent slow-wave structures known in the art, for example see U.S. Pat. Nos. 2,843,797 to Boyd and 2,860,280 to McArthur.

In the foregoing exemplary applications the electron beam is subject to some modulation whether velocity, density, or combinations thereof. The invention is broadly applicable to beam devices where the beam passing through a structure provides significant changes in an input signal and power output may be amplified or provided with desired oscillations. The log periodic circuit may be suitably adapted for forward or backward wave characteristics. In the backward wave type the input and output'ports are reversed and the input signal is introduced through the now input port 80 and power output is taken from the now power output port 80. Ordinarily the embodiment of FIG. 2 for example, a traveling wave helix type of circuit is more favorable for backward wave operation. In a reverse structure where the cathode is at the smaller end of the interaction structure, and the collector is at the larger end, the log factor becomes greater than one, from cathode to collector.

A further modification of this invention is illustrated in FIG. 3. Referring now to FIG. 3, there is disclosed a biconical device 86. Biconical device 86 includes a pair of log period sections 87 and 88, which are oppositely disposed and joined at their apex ends by an intermediate section 89 which may or may not contain interaction structure. Each section 87 or 88 may be of any of a number of different kinds of interaction circuit including for example a slow-wave circuit as the klystrontype circuit of FIG. land the traveling-wave-type helix circuit of FIG. 2, or combinations of different circuits. For purposes of further illustration sections 87 and 88 are shown as traveling-wave interdigital circuits of alternate ring or cylinder design. For example, in section 87 alternate annular elements 89, 90, 91 and 92 are connected to transmission line 93 while alternate annular elements 94, 95, 96 and 97 are connected to transmission line 98. Both transmission lines 93 and 98 are terminated at a single connector 99. Each section, in this example, is similar in construction so that the foregoing description is applicable to section 88 also. The sections, however, may in corporate different circuits as well as different log periodic factors.

In the device as illustrated in FIG. 3 section 87 is denoted as the input circuit section with input coupling 99, and section 88 is denoted as the output circuit section with output coupling 99'. The operation of the device of FIG. 3 as an RF amplifier is similar to other well-known backward wave amplifiers. For example, cathode structure 64 is suitably energized to provide an electron beam 100 passing through sections 87 and 88 and controlled in cross section by solenoid 101. An input signal in the form of an electromagnetic wave is coupled into connector 99 into transmission lines 93 and 98.

The input signal flows back toward cathode 64 until it reaches a region in section 87 where it is synchronous with the electron beam 100. A backward wave interaction at this region produces bunching of the electron beam, and the input or drive signal continues on until it reaches the region where the input is cut off. At this point it may be reflected or selectively absorbed. The distance from midplane of the device to the point where interaction takes place is directly proportional to the applied wavelength. Thus interaction at the longer wavelengths extends over a greater physical distance but the same electrical distance as interactions at shorter input signal, interaction takes place between the beam and the circuit and power is coupled out by transmission lines 93' and 98' at output connector 99'. The strongest interaction occurs at a distance from the midplane which is directly proportional to the operating wavelength. Thus in the biconical device the interaction at the lowest frequencies extends over essentially the entire length of the tube. As the frequency is increased the region of interaction moves in from each end towards the center of the tube.

The biconical device is adaptable for general klystron-type as well as other traveling wave tube-type configurations, or for combinations of different circuits where one or more different circuits may be applied to each biconical circuit section 87 or 88. Suitable examples of different circuits are illustrated in FIGS. 4, 5, 6 and 7 wherein biconical devices incorporate the circuits of FIGS. 1, 2 and 3. More specifically a half section or circuit in FIG. 3 is replaced with a traveling-wave circuit of FIG. 2, to provide the FIG. 4 embodiment. A cavity circuit of FIG. 1 replaces a half section of FIG. 3 to provide the FIG. 5 modification.

The biconical modifications of FIGS. 6 and 7 do not use different circuits in each half section. They employ the circuits of FIGS. 1 and 2 respectively for each half section. The biconical modifications, however involve circuits different from that of FIG. 3.

Best results are obtained in this invention when the log periodic factor as applied is applied uniformly. However, the log factor need not be the same for all parts to which it is applied. For example, the log periodic factor may be different for different axial sections and may alternate. Any application of a specific log factor should extend over a plurality of cavities at least three for example, and over an equivalent length of other interaction structure.

This invention thus describes the specific combination of a log periodic interaction structure whether of the cavity resonator type, magnetron type, vane type, or other known circuits, together with an electron beam passing through the device, where the beam selectively interacts with the interaction structure. In the operation of such a device the input frequency predeterminately selects its own cavity or cavities or a limited region of a helix or other interaction circuits for interaction. The location or position of the actual cavity or region of an interaction circuit which is selectively energized, may change or move along the interaction structure reversibly, dependent on input signal frequency. This may be described as a floating region along the interaction structure transiently localized by the particular frequency of the input signal.

The floating region may encompass one or more successive cavities of FIG. 1, a portion of the helix of FIG. 2, or successive rings of FIG. 3. In a resonant cavity device a given signal will provide effective response of one or more cavities for interaction energy exchange while other adjacent cavities may be only slightly or negligibly responsive. Where the beam coupies power to the circuit a similar region of cavities are defined. These regions may be in effect immediately following each other or they may be spaced apart by cavities of negligible or not response. The peak response of the two regions are spaced apart and their axial spacing is fixedly related to each other as depending on the frequency of the input signal, and both float as above defined. Both regions are adjacent in that no effectively responsive region is apparent therebetween. The operation is similar for traveling wave circuits such as helix circuits, interdigital circuits, etc. These latter circuits may be considered to be circuits periodically acting on or with an electron beam where each turn of a helix, or ring of an interdigital structure is defined as a period.

The log periodic principle is also applicable to extended log periodic arrays of such electron discharge devices as diodes, tetrodes, crossed field devices, etc. For example, an array of space charge devices such as tetrodes may be coupled to an input delay line having log periodic resonant circuits for each tetrode. Power output is obtained through a similar delay line also having log periodic resonant circuits for each tetrode.

While this invention has been described with reference to particular and exemplary embodiments thereof, it is to be understood that numerous changes can be made by those skilled in the art without actually departing from the invention as disclosed, and it is intended that the appended claims include all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

Iclaim:

l. A method of operation of an electron beam interaction device comprising:

a. passing an electron beam by a number of successive interaction regions whose successive interaction differences vary progressively in a log periodic manner;

b. introducing a predetermined power signal into said device for said signal to selectively energize one of a plurality of said regions for modulation of said beam;

c. causing said beam to couple power to other interaction regions; and

d. coupling a changed power out of said device from said other regions which are selectively energized by said beam and are in fixed separate relationship to said input signal.

2. An electron device comprising in combination:

a. a log periodic structure having successive portions varying from each other in a log periodic and frequencyresponsive manner to be selectively frequency responsive to input power signals;

b. input signal means coupling a plurality of said portions together so that signal power input selectively activates one of said circuit portions for energy exchange;

c. means transmitting said energy exchange to further portions of said circuit;

d. means to couple a changed power out of said structure at said further frequency-responsive portions thereof activated by and fixedly related to the frequency response of said first portion.

A log periodic amplifier comprising in combination:

a. an interaction structure having a first portion interacting with an electron beam at different successive regions having log periodic variances extending in one direction;

b. a second portion of said extended interaction structure having successive regions varying in a log periodic manner in a direction opposite to said one direction;

c. means to pass an electron beam into said structure for interaction therewith at said regions;

d. means to couple an input signal into said interaction structure so that said signal selectively energizes one of said successive interaction regions based on the input frequency of said signal;

e. means to couple amplified power out of said device from said second portion of said interaction structure; and

f. collector means to collect electrons in said beam after said interaction.

4. A log periodic power amplifier comprising in combination:

a. an extended interaction structure comprising a log periodic wave-supporting circuit for periodically interacting with an electron beam at different successive regions in a log periodic manner;

b. means to pass an electron beam into said structure for interaction therewith at one of said regions;

0. and means to couple an input signal into said circuit so that said signal selectively energizes one of said successive interaction regions based upon the input frequency of said signal for interaction with said beam and said beam couples amplified power .to said structure at another frequency responsive region depending on the frequency of said input signal;

. means to couple amplified power output from said structure; and

e. electron collector means to collect electrons in said beam after said interaction takes place.

5. The invention as recited in claim 4 wherein said interaction structure comprises an interdigital circuit.

6. The invention as recited in claim 4 wherein said interaction structure comprises at least in part an extended array of cavity resonators coupled together bysaid input signal means.

7. A log periodic amplifier comprising in combination:

a. an interaction structure having an axial array of cavity resonators each of which includes all significant dimensions smaller than the similar dimensions of a preceding cavity resonator so that said resonators vary in a log periodic manner along said array;

b. means to generate an electron beam passing through said interaction structure;

c. input signal means coupled to said resonators to introduce an input signal into said structure to selectively energize one of said resonators depending on the frequency of said input signal for bunching of said beam, and for said bunched beam to couple amplified power to said structure at other cavities depending on said input frequency;

d. means to couple amplified power out of said structure;

and

e. collector means to collect electrons from said beam after said interaction in said structures.

8. A log periodic amplifier comprising in combination:

a. an axially extending interaction structure defining an electron beam path therealong for interaction with an electron beam therein;

b. said interaction structure having regions therealong which are frequency responsive to predetermined different input signal frequencies;

c. said regions having interaction characteristics which vary in a log periodic manner with respect to an electron beam passing therethrough;

d. means generating an electron beam passing through said interaction structure;

e. means to couple an input power signal into said device for said signal to selectively energize one of a plurality of available input regions which is responsive to the frequency of said input signal; means to couple an amplified signal from said device from one of a plurality of available output regions the response of which is based upon the region selectively energized by said input signal; and

g. collector means on said structure and in said path to collect electrons in said beam after interaction in said structure.

9. The invention as recited in claim 8 wherein said input and output means are provided by a transmission line.

10. The invention as recited in claim 8,wherein said interaction structure comprises an axially extending array of cavity resonators whose interaction effect from interaction gap to succeeding interaction gaps progressively varies in a log periodic manner, said cavities being coupled together by said signal means, and said cavity resonators adapted to be coupled between said regions by said electron beam.

11. The invention as recited in claim 10 wherein said input and output means consists of a transmission line rod coupled to said cavities.

12. The invention as recited in claim 10 wherein each succeeding cavity resonator is smaller than its preceding cavity resonator in a log periodic progression with successively smaller interaction gaps in logarithmic progression to provide a ta ering interaction structure.

15. The invention as recited in claim 10 wherein said interaction structure is frustoconical over a substantial portion of its length.

14. The invention as recited in claim 8 wherein said interaction structure comprises an interdigital slow-wave RF transmission circuit.

15. The invention as recited in claim 14 wherein said interaction structure comprises a helix circuit.

16. The invention as recited in claim 15 wherein said helix tapers from a larger input end to a smaller output end.

17. The invention as recited in claim 15 wherein said helix is frustoconical.

18. The invention as recited in claim 15 wherein the turn density of said helix increases toward said smaller end.

19. The invention as recited in claim 3 wherein said interaction structure includes at least in part, a plurality of reentrant cavity resonators which are coupled to one of said signal means.

20. The invention as recited in claim 19 wherein at least three reentrant cavity resonators are employed.

21. A log periodic amplifier comprising in combination:

a. a pair of electrically tapered log periodic interaction structures;

b. means joining said structures at their smaller ends;

c. said structures defining an electron beam path therethrough for interaction of an electron beam with said structures;

d. input signal means at one end of one of said structures;

e. output means at the one end of the other of said structures;

f. electron beam generating means to generate an electron beam to pass along said path; and

g. electron collector means on said structure and in said path to collect electrons from said beam after said interaction takes place in said structure.

22. The invention as recited in claim 21 wherein said electrically tapered structures include frustoconical structures joined at their smaller ends.

23. The invention as recited in claim 22 wherein said joining includes a cylindrical intermediate structure.

24. The invention as recited in claim 23 wherein one of said structures includes an array of reentrant cavity resonators coupled to said signal means.

25. The invention as recited in claim 24 wherein one of said structures includes a traveling-wave helix interaction structure.

26. The invention as recited in claim 24 wherein both structures consist of an extended array ofreentrant cavity resonators coupled to said signal means.

27. The invention as recited in claim 25 wherein both of said structures consist of a traveling-wave tube helix interaction circuit. 

1. A method of operation of an electron beam interaction device comprising: a. passing an electron beam by a number of successive interaction regions whose successive interaction differences vary progressively in a log periodic manner; b. introducing a predetermined power signal into said device for said signal to selectively energize one of a plurality of said regions for modulation of said beam; c. causing said beam to couple power to other interaction regions; and d. coupling a changed power out of said device from said other regions which are selectively energized by said beam and are in fixed separate relationship to said input signal.
 2. An electron device comprising in combination: a. a log periodic structure having successive portions varying from each other in a log periodic and frequency-responsive manner to be selectively frequency responsive to input power signals; b. input signal means coupling a plurality of said portions together so that signal power input selectively activates one of said circuit portions for energy exchange; c. means transmitting said energy exchange to further portions of said circuit; d. means to couple a changed power out of said structure at said further frequency-responsive portions thereof activated by and fixedly related to the frequency response of said first portion.
 3. A log periodic amplifier comprising in combination: a. an interaction structure having a first portion interacting with an electron beam at different successive regions having log periodic variances extending in one direction; b. a second portion of said extended interaction structure having successive regions varying in a log periodic manner in a direction opposite to said one direction; c. means to pass an electron beam into said structure for interaction therewith at said regions; d. means to couple an input signal into said interaction structure so that said signal selectively energizes one of said successive interaction regions based on the input frequency of said signal; e. means to couple amplified power out of said device from said second portion of said interaction structure; and f. collector means to collect electrons in said beam after said interaction.
 4. A log periodic power amplifier comprising in combination: a. an extended interaction structure comprising a log periodic wave-supporting circuit for periodically interacting with an electron beam at different successive regions in a log periodic manner; b. means to pass an electron beam into said structure for interaction therewith at one of said regions; c. and means to couple an input signal into said circuit so that said signal selectively energizes one of said successive interaction regions based upon the input frequency of said signal for interaction with said beam and said beam couples amplified power to said structure at another frequency responsive region depending on the frequency of said input signal; d. means to couple amplified power output from said structure; and e. electron collector means to collect electrons in said beam after said interaction takes place.
 5. The invention as recited in claim 4 wherein said interaction structure comprisEs an interdigital circuit.
 6. The invention as recited in claim 4 wherein said interaction structure comprises at least in part an extended array of cavity resonators coupled together by said input signal means.
 7. A log periodic amplifier comprising in combination: a. an interaction structure having an axial array of cavity resonators each of which includes all significant dimensions smaller than the similar dimensions of a preceding cavity resonator so that said resonators vary in a log periodic manner along said array; b. means to generate an electron beam passing through said interaction structure; c. input signal means coupled to said resonators to introduce an input signal into said structure to selectively energize one of said resonators depending on the frequency of said input signal for bunching of said beam, and for said bunched beam to couple amplified power to said structure at other cavities depending on said input frequency; d. means to couple amplified power out of said structure; and e. collector means to collect electrons from said beam after said interaction in said structures.
 8. A log periodic amplifier comprising in combination: a. an axially extending interaction structure defining an electron beam path therealong for interaction with an electron beam therein; b. said interaction structure having regions therealong which are frequency responsive to predetermined different input signal frequencies; c. said regions having interaction characteristics which vary in a log periodic manner with respect to an electron beam passing therethrough; d. means generating an electron beam passing through said interaction structure; e. means to couple an input power signal into said device for said signal to selectively energize one of a plurality of available input regions which is responsive to the frequency of said input signal; f. means to couple an amplified signal from said device from one of a plurality of available output regions the response of which is based upon the region selectively energized by said input signal; and g. collector means on said structure and in said path to collect electrons in said beam after interaction in said structure.
 9. The invention as recited in claim 8 wherein said input and output means are provided by a transmission line.
 10. The invention as recited in claim 8 wherein said interaction structure comprises an axially extending array of cavity resonators whose interaction effect from interaction gap to succeeding interaction gaps progressively varies in a log periodic manner, said cavities being coupled together by said signal means, and said cavity resonators adapted to be coupled between said regions by said electron beam.
 11. The invention as recited in claim 10 wherein said input and output means consists of a transmission line rod coupled to said cavities.
 12. The invention as recited in claim 10 wherein each succeeding cavity resonator is smaller than its preceding cavity resonator in a log periodic progression with successively smaller interaction gaps in logarithmic progression to provide a tapering interaction structure.
 13. The invention as recited in claim 10 wherein said interaction structure is frustoconical over a substantial portion of its length.
 14. The invention as recited in claim 8 wherein said interaction structure comprises an interdigital slow-wave RF transmission circuit.
 15. The invention as recited in claim 14 wherein said interaction structure comprises a helix circuit.
 16. The invention as recited in claim 15 wherein said helix tapers from a larger input end to a smaller output end.
 17. The invention as recited in claim 15 wherein said helix is frustoconical.
 18. The invention as recited in claim 15 wherein the turn density of said helix increases toward said smaller end.
 19. The invention as recited in claim 8 wherein said interaction structure includes at least in part, a plurality of reentrAnt cavity resonators which are coupled to one of said signal means.
 20. The invention as recited in claim 19 wherein at least three reentrant cavity resonators are employed.
 21. A log periodic amplifier comprising in combination: a. a pair of electrically tapered log periodic interaction structures; b. means joining said structures at their smaller ends; c. said structures defining an electron beam path therethrough for interaction of an electron beam with said structures; d. input signal means at one end of one of said structures; e. output means at the one end of the other of said structures; f. electron beam generating means to generate an electron beam to pass along said path; and g. electron collector means on said structure and in said path to collect electrons from said beam after said interaction takes place in said structure.
 22. The invention as recited in claim 21 wherein said electrically tapered structures include frustoconical structures joined at their smaller ends.
 23. The invention as recited in claim 22 wherein said joining includes a cylindrical intermediate structure.
 24. The invention as recited in claim 23 wherein one of said structures includes an array of reentrant cavity resonators coupled to said signal means.
 25. The invention as recited in claim 24 wherein one of said structures includes a traveling-wave helix interaction structure.
 26. The invention as recited in claim 24 wherein both structures consist of an extended array of reentrant cavity resonators coupled to said signal means.
 27. The invention as recited in claim 25 wherein both of said structures consist of a traveling-wave tube helix interaction circuit. 